Voice over Internet Protocol (VoIP) enables users to make telephone calls over a computer network, such as the Internet. VoIP is used to convert a voice signal from a telephone into a digital signal, which can be transmitted over the computer network. At a receiving end, VoIP is used to convert the digital signal back into a voice signal.
SIP is a signaling protocol for VoIP. In particular, SIP is a request/response protocol that allows devices to set up a communication session over a network. Real-time transport protocol (RTP) is typically used during the communication session to carry voice and other data between the devices on the network.
Problems can arise during transmission of telephone calls over a network. For example, excessive network traffic can create a bottleneck at a node on the network, thereby affecting the quality of telephone calls transmitted through the node. Also, a node on the network can fail or function improperly, which can also have a deleterious effect on telephone calls transmitted through the network. These problems are not unique to telephone calls that are implemented using VoIP (e.g., telephone calls routed over a computer network), but rather such problems can occur in any network over which telephone calls are routed.